Oxidation of lower aliphatic alcohols



' Aug.19,f1947. D. c. HULL 2,425,880

oxIbA'rIon or Loman ALIPHATIc AncoaoLS mea .my a. 1944 Patented' Aug.' 19, 1947 David C. Hull,

OF LOWER ALIPHATIC ALCOHOLS Kingsport, Tenn.. assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Appueation July 4s. 1944, sei-iai No. 544,001

l 5 Claims. This invention relates to the direct loxidation of organic compounds, particularly the oxidation of hydroxy compounds such as lower aliphatic alcohols oxidized directly to acids. As pointed out in my U. S. Patent No. 2,287,803 prior art oxidation processes have required the such as 300 C. or 400 C. and the application of several steps. In other words, the loxidation either has not been direct, or if there has been direct conversion, the yields have been very low.

For example, considering prior art procedure for converting ethanol to acetic acid, before my invention it was considered necessary to first dehydrogenate all of the ethanol and thereafter the aldehydic dehydrogenation product was converted to the acid which, as can be seen, involves a number of steps.

Carrying out oxidation processes in accordance with the prior. art possesses a number of disadvantages exemplified, for example, by the required use oi' 'relatively high temperatures. Also there may in some instances be the disadvantage of polymerization of the products and of the starting materials accompaniedfby low -yields and other losses.

In my U. S. Patent 2,287,803 I have described a process for a more direct oxidation of organic compounds. While the process of my application functions very satisfactorily and' gives good yields in relatively few steps, it involves the utilization of metals having an atomic number from 25 to 29. It is, therefore apparent that it is desirable, particularly under present conditions, to develop a process in order that other metals may be employed and the process improved in other respects, as will be apparent from the description which follows.

After further investigation I have found that there are certain other catalytic materials which may be employed in direct oxidation processes in a manner akin to the procedure set forth in my U. S. Patent 2,287,803 which, not only permits obtaining direct "oxidation, but permits the production of a relatively larger variety of products than has heretofore been obtainable.

This invention has for one object to provide a process for the direct oxidation of organic compounds. Another object is4 to provide a direct oxidation process which is particularly valuable for the direct conversion of lower aliphatic alcohols to lower aliphatic acids in substantially a single step. Still another object, however, is to provide a process which may also .be applied to.

.- 2 polyhydroxy alcohols V and other similar organic compounds. Another-and particular object of this invention is to provide a direct oxidation employment of relatively high temperatures process which may be operated -at relatively low temperatures and under ordinary pressure conditions, yet give very satisfactory yields' of the desired oxidation products. Still another object is. to provide a direct oxidation process for the.

conversion of alcohols to acids wherein the alcohol may be converted, not only to an acid having a number of carbon atoms corresponding to the number of carbon atoms in the alcohol molecule, but also to a different acid. A still further object is to provide a process which 'may be opeated under other than normal atmospheric conditions, nameiy,`under either superatmospheric or reduced pressures.

A further object is to provide a direct oxidation processthat may be applied to eitherA alcohols alone or mixtures of alcohols and aldehydes, or other types of mixtures. A' still further ob'- ject is to provide a direct, low-temperature oxinot only the monohydroxy alcohols, .but to the 68 dation process which may be applied to various mixtures of alcohols and aldehydes wherein both the alcohol and the aldehyde are converted into useful oxidation products. Another object is to provide a direct oxidation process, particularly adapted to the treatment of alcohols such as butyl alcohol and the like wherein, not only may butyric acid be obtained, but contents of other acids.

A further object is to provide novel catalysts containing liquids particularly adapted for em.- ploym'ent'in the aforesaid types of processes for ,the direct conversion of alcohols along, or alco- 'hols in various admixtures, into useful oxidation products. Al still further object is to provide methods for producing the catalysts as well as Vfor activating and utilizing the catalysts.

As already indicated, prior to my invention if an alcohol were to be oxidized it was generally first dehydrogenated and then the dehydrogenation products further treated.l In any event prior' art processes as applied to alcohols usually involve the utilization of temperatures in excess of 300 C., which, not onlyrequires substantial heat input'but, dueto the `higher temperatures and other conditions required in handling chemical's, involves dangers of loss from polymerization or other undesired reactions. Also apparatus destruction maybel more severe.

I have found that contrary to such procedure an organic compound, exemplified in particular by a hydroxy compound as a lower aliphatic alcohol, maybe directly oxidized at relatively low temperatures, even temperatures substantially below 100 C., with any of the usual oxidizing mediums of which the commonest one, namely air, may be readily utilized in my process. Also my process, after it is placed in operation, does not usually require any heat .input but generates sufficient heat itself to maintain the reaction. Not only may single organic compounds be treated, but various mixtures of the organic compounds may be treated. For example, I have found that a mixture comprising a lower aliphatic alcohol, together with a corresponding or a different aldehyde, may be efficiently treated by my novel process and catalyst to give very high yields of aliphatic acid. By my\process and choice of catalyst it is possible to obtain one or more acids in the oxidation procedure. The foregoing features, as well as features of treating various mixtures under different conditions, will be set forth in detail hereinafter.

While the oxidation procedure may be carried out in the apparatus described in my U. S. Patent No, 2,287,803, for convenience of consideration and for a better understanding of the present invention reference will be made to the attached drawing. The single figure thereof may be considered a semi-,diagrammatic side elevation view showing a general apparatus arrangement which could be employed for carrying out my process.

Referring to the drawing, 2 represents an oxida tion unitwhich maycomprise anyof several differ-l ent constructions. For example, the preferred external construction would, in a large diameter unit, be in accordance with Haschey Patent 2,159,988. However, the construction may be a sieve plate column, bubble plate column, or other comparable arrangement for permitting the contact of an oxidizing medium containing free oxygen with the material to be oxidized. In the unit shown in the attached gure the column merely comprises an elongated, o pen columny of relatively narrow dimensions. Attached to the lower part of the unit at 3 and 4, are cooling jackets provided with inlets for cooling medium as at 6 and 1. l

The upper part of the unit was provided with a similar jacket 8; however, in this jacket, rather than cooling medium some heating medium mayl be circulated in the eventthat high boiling components are being directly oxidized or the reaction Atemperature is to be held lower than that which would maintain a constant volume of catalyst. Inasmuch as the construction is substantially the same, however, the mechanical construction would be approximately the same and an inlet provided at 9, 1 and 6; outlets are provided at II, I2, and I3.

As indicated, if desired in place of the external jackets, coils may be included within the unit and in large-size units such arrangement wherein internal coils, or both coils and jackets are employed, may be desirable.

The lower part of the unit is provided with a plurality of inlet' conduits, namely, inlet conduit I4 which is connected with a temperature-controlled feed supply I6. Also leading into the lower part of the unit is an inlet conduit I1 for oxidizing medium.

The upper part of the unit is provided with a drawoff conduit IB which leads through condenser I9 into separator 2 I. This separator has attached thereto a receiver 22 for condensate and a branch 'conduit 23 through which non-condensables may be conducted to the scrubber 24.

The aforementioned scrubber is provided with a receiver 26 at the lower part thereof and vent conduit. 21 from the upper part thereof, which may lead through a meter or other device for measuring and testing the elllue'nts.

There may also be associated with the apparatus thermometers or other temperature controlling devices or various exchangers for recovering heat or otherwise facilitating or rendering the operation of the process more economical, or permitting it to be operated with automatic control. Hence, my invention is not to be restricted in these respects.

I have found that certain metal compounds, as for example, salts derived from the metals of group II of the periodic table included in the group consisting of cadmium, mercury and zinc may be incorporated in acidicsolutions and that these solutions will function as a catalyst medium for the direct oxidation of organic compounds. That is, an alcohol alone or an alcohol and other organic compounds to be oxidized, may be passed into a catalyst solution, as aforementioned, in the presence of an oxidizing medium containing free oxygen and the alcohol may be directly oxidized to acid, as will be observable from the specific data which follow.

In preparing catalyst solutions for use in the present process, any convenient source of the metal may be employed, such as salts, oxides, or other derivatives thereof. Preferably a derivative will be chosen which is easily soluble under the conditions of the process. For example, assuming that itis desired to convert an aliphatic alcohol such as ethanol or butanol directly to the corresponding aliphatic acid the derivative of the catalyst metal may be a compound such as cadmium acetate,mercuryacetatev or zinc acetate.

While the aforementioned metal derivative may be employed in various organic liquids, which are solvents therefor, for simplicity of operation and minimizing the necessity of complicated separations I prefer to dissolve the catalyst compound in a liquid principally composed of one of the materials which is to be produced in the process. For example, in the event my ,process were to be applied in converting butyl alcohol directly Into butyric acid I, would preferably dissolve the catalyst compound in an aliphatic acid such as butyric acid, although propionic or acetic acid could also lbe used. However, for initially preparing the catalyst solution other liquids could be employed, as for example, organic esters and the like such as butyl or ethyl acetate.

In any event, irrespective of the exact metal compound and the liquid that the compound is dissolved in, the catalyst solution would be given a vigorous oxidation treatment such as blowing with a substantial amount of air, usually for a period of at least 5 or 10 minutes, and if desired,

for several hours. This treatment would be accompanied by the introduction of an aldehyde along with the oxidizing medium which functions to convert the metal ions of the catalyst metal into a higher state of valence than their lowest atmospheric pressure as this permits the inclu sion of a larger amount of oxidizing medium and fully saturates the catalyst liquid.

After the catalyst liquid containing a group II `As indicated, while at normal atmospheric pressure, a temperature under 100 C. appears to be quite satisfactory, the particular temperature selected will be determined largely by reference to In` the above examples, there was some small percentage of alcohol converted to acetic acid and some butyl esters in addition to the main product of the oxidation, while the major portion f the remaining alcohol was leit unchanged. 1|

metal compound as already described has been the particular alcohol to be oxidized, and whether treated and brought yto a starting temperature, the process is to be operated under pressure or usually above room temperature but below about merely at atmospheric pressure. For example, 100 C., the organic compound to be oxidizedmay although I find a temperature range lof 5 C. to be supplied to the process. 90 C. satisfactory, for the oxidation of butyl al- Thatfis, referring to the attached drawing, the l0 coholto butyric acid, if ethyl, propyl alcohol is oxidation column 2 is filled with the catalyst to be converted by my process, with or without liquid comprising one or more of the group II butyl alcohol, `I prefer a` temperature range of metal compounds ofthe type described dissolved 30 to 50 C. in the solvent and maintainedat the desired tem/- Under preferred operating conditions as, for Derature. The hydroxy compound to be oxidized example, when air is used asthe oxidant, this is introduced into the oxidation process through may be supplied under some pressure, and, if deconduit Il and the oxidizing medium, usually sired, a rather substantial excess may be emair (although pure oxygen or ozone may be employed, although for normal operations merely an ployed and appear to render the catalyst soluexcess is required; that is, such an amount that tion more active, butare not necessary), and the a few percent of oxygen will be present in the compound oxidized to one or more desired oxidaeffluents. In the event of the .use of other oxition products, as will be described hereinafter. dants such as relatively pure oxygen and ozone Assuming that the oxidation product is' aliquid, smaller amounts are required and may be supa portion thereof may be volatilized or pumped fplied under substantial pressure to cause them oil through conduit I8 through the condenser I9 25 fully .to permeate the entire catalyst solution. where condensables are condensed out to be col- The oxidation oi any given alcohol in accordlected inreceiver 22. The unconsumed gases (as ance witnmy process may be accomplished by nitrogen when air is used as oxidizing medium), activating the catalyst metal in the solution by unoxidized organic compounds and the like cornmeans of a single aldehyde or by a plurality of ponents, uncondensed, pass through conduit 23 30 aldehydes. For example, in OXidiZing ethyl a1- into scrubber 24 where they are recovered. While cohol, I may employ acetaldehyde, propionaldeonly a single scrubbing unit has been indicated, hyde, or bntyraldehyde alone or two or more ofa plurality of such units may be employed or them. Moreover, I may oxidize ethyl alcohol, other recovery devices utilized. l propyl alcohol, butyl alcohol, or amyl alcohol, by

'Ihe opera-tion of my process to convert an or- 35 employing any one or more of aldehydes such as ganic compound such as ethyl alcohol.. prop yl acetaldehyde, propionaldehyde, butyraldehyde, nlcOhOl, butyl alCOhOl, 0r other aliphatic hydroxy and so on. However, inasmuch as acetaldehyde compounds tothe desired acids and the function i isl in many instances most readily available andof the group 1I metals as aldehyde activated has a low boiling point, it would preferably be catalysts is quite clearly illustrated by the data 40 employed along with other alcohols such as butyl appearing in 'the following table: 'Y alcohol, amyl alcohol, and the like, as represent- Metalxcetate Nielaclegn Glfgslgfyl (lalliiii gbagl iirgrlirs cfvgilin cmg-imn in Cat. .SOL Feed Prod. Prod. to HOBu to HOPr Mercury. 5 281 aso 100.4 41.9 29.4 14.6

The foregoing examples were carried out in in g the most economical procedure, as well vas apparatus as indicated in the attached drawing tending to`low`er the boiling points and permit and at a temperature between 30 C. and 50 C., the functioning of the process at the lowest pracalthough a wider range of temperatures, such as tical temperatures. -5 C. to 90 C. could be employed satisfactorily. As already indicated, the pressure maybe varied It will be observed from the above table that I over wide limits without basically changing the have employed a relatively small amount of the DIGCGSS- HOWeVe'r, Since the DIOCBSS functions metal acetate in the catalyst solution in the exsatisfactorily under normal atmospheric presamples given, but this may be .varied rather sures, I prefer to operate under such conditions. I widely. For example, I may use anywhere from In some instances, such as for saturating the l or 2% of the metal acetate up to-12% or more. 00 catalyst solution withoxygen, I may apply a few Whilethe foregoing examples are illustrative pounds pressure up to 2, or 3 atmospheres for this of preferred embodiments of my invention, it will purpose. A180,` aS. indicated, the process funcbe evident that many modiilcationstherein may tions very well at temperatures Vof 5 C. to 50 be made within the scope of the inventive con.. or 70 C. and normal atmospheric pressure. Howcept involved. As previously indicated, these 55 over, #by raising the temperature above-the range catalysts may be used underthe conditions outindicated t0 90 C, fOr example, .the PIGSSUIB lined above for the conversion of various aliphatic Should be increased in order to assure a suillcient alcohols tc acids. They may be employedin the supply of aldehyde -in the catalyst solution to obform of a single salt or mixtures of salts of any tain .the desired catalyst activity. By` operating desired organic acid or acids. 7o at these higher temperatures and pressures, larger amounts of alcohol may be converted per'pass per unit of time. Under .such procedure the alde hyde feed would be correspondingly reduced as the amount of alcohol fed was increased. In

general, it may be said that I prefer to carry out the processunder liquid phase conditions and at a temperature of 30 C. to 70 C.

One valuable aspect of the present invention is that acids having fewer carbon atoms than the alcohol being oxidized may be directly produced, and the 'proportion of these other acids to the acid having the same number of carbon atoms as the alcohol being oxidized may be varied by choice of the particular catalyst.

It is apparent from the foregoing that my invention is applicable to the direct oxidation of the various organic compounds, particularly hydroxy compounds such as various alcohols. The foregoing data are merely illustrative of some of the materials to which my low temperature liquid phase process may be applied, but various other compounds, such as hydroxy alcohols exempliiied by glycols, may be treated in a comparable manner. Hence, I do not wish to be restricted in my invention except insofar as is necessitated by the prior art and the Spirit of the appended claims.

What I claim and desire to secure by Letters' Patent of the United States is:

1. A process for the direct oxidation of a lower aliphatic alcohol to obtain the corresponding aliphatic acid, which comprises treating a solution of a metal ion of a group II metal selected from the group consisting of cadmium, mercury and zinc in an alaphatic acid with an aldehyde and a gaseous oxidizing medium to form an active catalyst solution, introducing material amounts of a lower aliphatic alcohol fand a lower aliphatic aldehyde into the activated catalyst solution, oxidizing the alcohol of the resulting solution of catalyst, alcohol and aldehyde to the corresponding acid by treating said solution with a gaseous oxidizing medium, maintaining the temperature of the solution of catalyst, alcohol and aldehyde during its treatment with the gaseous oxidizing medium such that the solution is maintained in the liquid phase, and subsequently recovering the aliphatic acid produced.

2'. A process for the direct oxidation of a lower aliphatic alcohol to obtain the corresponding aliphatic acid, which comprises treating a solution of a metal ion of a group II metal selected from the group consisting of cadmium, mercury and zinc A in an aliphatic acid with an aldehyde and a gaseous oxidizing medium to form an active catalyst solution, introducing material amounts of a lower aliphatic alcohol and a lower aliphatic aldehyde into the activated catalyst solution, oxidizing the alcohol of the resulting solution of catalyst, alcohol and aldehyde to the corresponding acid by treating said solution with a gaseous oxidizing medium, maintaining the temperature of the solution of catalyst, alcohol and aldehyde during its treatment with the gaseous oxidizing medium such that the solution is maintained in the liquid phase at a temperature of from 5 C. to 100 C.,

yand subsequently recovering the aliphatic acid aldehyde and a gaseous oxidizing medium to formv an active catalyst solution, introducing material amounts of a lower aliphatic alcohol and a lower aliphatic aldehyde into the activated catalyst solution, oxidizing the alcohol ot the resulting solution of catalyst, alcohol and aldehyde to the corresponding acid by treating said solution with a gaseous oxidizing medium, maintaining the temperature of the solution of catalyst, alcohol and aldehyde during its treatment with the gaseous oxidizing medium at a temperature such that the solution is maintained in the liquid phase below 100 C., and subsequently recovering the aliphatic acid produced.

5. A process for the direct oxidation of a lower aliphatic alcohol to obtain an acid mixture containing a major proportion of an acid corresponding to the alcohol being oxidized and a minor proportion of an acid having a less number of carbon atoms than the alcohol, which comprises treating a solution of a metal ion of a group II4 metal selected from the group consisting of cadmium, mercury, and zinc in'an aliphatic acid with' an aldehyde and a gaseous oxidizing medium to form an active catalyst solution, introducing material amounts of a lower aliphatic alcohol and a lower aliphatic aldehyde into the activated catalyst solution,l oxidizing the alcohol of the resulting solution of catalyst, alcohol and aldehyde by treating said solution with a gaseous oxidizing medium, maintaining the temperature of the solution of catalyst, alcohol and aldehyde during its treatment with the gaseous oxidizing medium such that the solution is maintained in the liquid phase at a temperature of 5 C. to 150 C., and subsequently recovering the aliphatic acid produced.

DAVID C. HULL.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS 

